Suddenly my interview reached its end. The Brother told me that he would see me again tomorrow. He stared at the young priest for a moment, said something in Arabian, then instructed him in Greek to conduct me to my lodging. I understood that all too well: I had been released on parole. I was being watched. I would not be permitted to inspect places they wished to keep secret. I would not be allowed free talk with the populace. Meanwhile, a decision on whether or not to let me leave Petra would be taken without my knowledge and without leave to appeal.

From now on, the Chief Minister would always know where I was. All my movements and even my continued existence, were at his whim. In fact, it struck me he was the sort of unreliable potentate who could well send me off now with a smile and a promise of mint tea and sesame cakes tomorrow – then dispatch his executioner after me in half an hour's time.

I was escorted from the sanctuary. I had no idea what was intended for the corpse. I never did find out what happened to it.

But that would not be my last connection with the man I had found on the High Place of Sacrifice.

Helena was waiting in our room. Expecting trouble, she had dressed her hair neatly in a decorated net, though she covered it demurely with a white stole when we entered. Discreet strands of beads were evenly hung on her fine bosom; hints of gold glinted at the tips of her ears. She was sitting very upright. Her hands were folded; her ankles crossed. She looked severe and expectant. There was a stillness about her that spoke of quality.

'This is Helena Justina,' I informed the young priest, as if he ought to treat her respectfully. 'I am Didius Falco, as you know. And you are?'

This time he could not ignore it. 'My name is Musa.'

'We have been adopted as personal guests of The Brother,' I stated, for Helena's benefit. Maybe I could impose duties of hospitality on the priest. (Maybe not.) 'Musa, at The Brother's request, is to look after us while we are in Petra.'

I could see that Helena understood.

Now we all knew everyone. All we had to do was communicate. 'How are we off for languages?' I asked, making it a matter of politeness. I was wondering how to shake Musa loose and drag Helena safely out of here. 'Helena is fluent in Greek; she used to kidnap her brothers' tutor. Musa speaks Greek, Arabic and I presume Aramaic. My Latin's low class but I can insult an Athenian, read the price-list in a Gallic inn or ask what's for breakfast of a Celt: Let's stick with Greek,' I offered gallantly, then switched to Latin, using an impenetrable street dialect. 'What's the news, beautiful?' I asked Helena, as if I were accosting her in an Aventine fish market. Even if Musa understood more Latin than he was letting on, this ought to fool him. The only problem was, a respectable young noblewoman born in a Capena Gate mansion might not understand me either.

I helped Helena unpack some olives we had bought earlier that day; it seemed like weeks ago.

Helena busied herself dividing salad into bowls. She replied to me off-handedly as if discussing dressed beans and chickpeas: 'When I came down from the High Place, I reported what had happened to a man who looked in authority who was standing outside the theatre – ' She peered at some strangely white cheeses.

'Ewe's milk,' I said cheerfully, in Greek. 'Or camel's!' I was not sure that was possible.

'People nearby must have been listening in,' Helena continued. 'I overheard speculation from a company of actors that the drowned man might belong to them, but I was so exhausted I just said they could contact you if they wanted more information. They seemed an odd lot; I don't know if we'll hear from them. The official collected his favourite cronies and went up to see about the body.'

'I saw it later,' I confirmed.

'Well, I left them to it and slipped away.'

We sat on rugs and cushions. Our Nabataean guardian seemed shy of small talk. Helena and I had a lot to think about; the apparent murder at the High Place had upset both of us, and we knew we were in a sticky predicament as a result. I stared into my supper bowl.

'Didius Falco, you have three radishes, seven olives, two lettuce leaves and a piece of cheese!' listed Helena, as if I was checking the equality of our rations. 'I divided it fairly, so there would be no quarrelling:'

She had spoken Greek herself this time as a courtesy to our silent guest. I switched back to Latin, like the man of the house being stubborn. 'Well, that's probably the last we'll hear of the drowned man, but you will gather you and I are now the subject of a tense political incident.'

'Can we shed this overseer?' she queried in our own tongue, smiling graciously at Musa and serving him the burned segment of our flat Petran loaf.

'Afraid he sticks.' I spooned him some mashed chickpeas.

Musa politely accepted our offerings, though with a worried air. He took what he was given – then did not eat. He probably knew he was the subject under discussion, and given the brevity of his instructions from The Brother he may have been feeling anxious about being alone with two dangerous criminals.

We tucked in. I wasn't his foster-mother. If Musa chose to be picky, as far as I was concerned he could starve. But I wanted my strength.

Knocking summoned us to the door. We found a gang of Nabataeans who did not look like passing lamp-oil salesmen; they were armed and determined. They started jabbering excitedly. Musa had followed us to the threshold; I could tell he disliked what he heard.

'You have to go,' he told me. His startled tone seemed genuine.

'Leave Petra?' It was amazing these people managed to conduct so much lucrative commerce if everyone who came to their city got sent away so promptly. Still, it could have been worse. I had been expecting The Brother to decide we should stay – probably in custody. In fact I had been pondering ways I could sneak us down the Siq to collect our ox-cart from the caravanserai in secret, then dash for freedom. 'We'll pack!' I volunteered eagerly. Helena had jumped up and was already doing it. 'So this is goodbye, Musa!'

'Oh no,' replied the priest, with an earnest expression. 'I was told to stay with you. If you leave Petra, I shall have to come.'

I patted his shoulder. We had no time to waste in argument. 'If we're being asked to leave, no doubt somebody forgot to countermand your orders.' He was unimpressed with this reasoning. I didn't believe it myself. If my corns had been in The Brother's boots, I too would have made sure an underling followed us to the Nabataean borders and put us firmly on board ship. 'Well, it's your decision.'

Helena was used to me acquiring eccentric travel companions, but looked as if this one had stretched her tolerance. Grinning unconvincingly, I tried to reassure her: 'He won't come with us far; he'll miss his mountains.'

Helena smiled wearily. 'Don't worry. I'm quite used to handling men I could do without!'

With as much dignity as we could muster we allowed ourselves to be marched out of Petra. From shadows among the rocks, dark figures watched us leave. The odd camel did us the honour of spitting after us disparagingly.

Once we stopped. Musa spoke almost crossly to the armed escort. They didn't like waiting, but he darted into a house and came back with a small baggage roll. Equipped with Nabataean underwear and toothpicks, presumably, we were hurried on.

By then night had fallen, so our journey took place by the light of flares. Their pallid flames flickered eerily on the lower carvings of the rock tombs, sending long shadows up the sandstone. Columns and pediments were glimpsed, then quickly lost. Square-topped doorways assumed a menacing air, their openings like mysterious black cave mouths. We were on foot. We let the Nabataeans carry our baggage across the city, but when we reached the narrow gorge through the mountains it was clear we were being sent on alone – almost. Musa definitely intended to stick all the way. To reach the outside world, I had to grapple with our baggage while Helena lit our way with a flaming brand. As she strode ahead of us in high annoyance, she looked like some devastating sibyl leading the way down a cleft into Hades.